Method for forming a sleeve for insulating a joint of downhole tubing

ABSTRACT

A method for forming a sleeve for wrapping around and insulating a joint of a downhole tubing string is provided. The method includes the steps of providing a mold, applying insulation around the mold, winding an interfacing material around the insulation; and applying a polymer onto the interfacing material to bind to the interfacing material to form the sleeve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/244,993 filed on Jan. 10, 2019, which claims priority to U.S.Provisional Patent Application Ser. No. 62/754,580 filed on Nov. 1,2018, the entire disclosures of which are incorporated herein byreference.

BACKGROUND

1. Paraffin and Wax Control.

Most produced oil has a certain number of heavy ends which consist ofwax and paraffins. As the well is produced the temperature drops to apoint when the wax and/or paraffins precipitate out (depending on thecloud point temperature) which can form on the tubing and plug and orstop the production.

2. Steam Transfer from Surface to the Reservoir.

-   -   In a SAGD application steam is generated at surface and pumped        down hole to the formation to heat the oil sands (high        viscosity) and lower the viscosity so that it can be produced        and pumped by an artificial lift method via a pump.        -   In order to deal with these or other issues, it is therefore            desired to have insulation for downhole tubulars.

SUMMARY

There is provided a tubular for downhole use, including a pipe, aninsulation layer surrounding the pipe, and a protective layer around theinsulation layer, the protective layer comprising a polymer. Theprotective layer may also comprise a compression layer adjacent to theinsulation layer. The compression layer may comprise 2-way tape. Theelastomer may be applied to the compression layer to bind to thecompression layer. There may be a reinforcement material within theprotective layer. The reinforcement material may be at least in part incontact with the compression layer. The elastomer may be applied overthe reinforcement material to encapsulate the reinforcement material.The reinforcement material may include a wire, rope, cord or strip. Thewire, rope, cord or strip may comprise one or more of metallic wire,carbon fibre, kevlar, fibreglass, or thermoform monofilaments.

The insulation layer may comprise aerogel or any other suitableinsulation, for example, fibre glass, rock wool, cellulose, vermiculite,perlite, polystyrene, Polyisocyanurate, polyethylene, or phenolic resin.The polymer may comprise an elastomer.

There is also provided a sleeve for wrapping around and insulating ajoint of a downhole tubing string, the sleeve comprising an insulationlayer; and a protective layer comprising a polymer, the protective layersurrounding the insulation layer when the sleeve is wrapped around thejoint. The protective layer may also include an interfacing layeradjacent to the insulation layer. The interfacing layer may comprise2-way tape. The polymer may be applied onto the interfacing layer tobind to the interfacing layer. There may be reinforcement materialwithin the protective layer. The reinforcement material may be at leastin part in contact with the interfacing layer. The polymer may beapplied over the reinforcement material to encapsulate the reinforcementmaterial. The reinforcement material may include a wire, rope, cord orstrip. The wire, rope, cord or strip may comprise one or more ofmetallic wire, carbon fibre, kevlar, fibreglass, or thermoformmonofilament. The insulation layer may comprise aerogel or any othersuitable insulation. The polymer may comprise an elastomer. The sleevemay include a base layer adjacent to the tubing string when the sleeveis wrapped around the joint, the polymer being applied onto at least anend of the sleeve to bind to the base layer at the at least an end ofthe sleeve.

There is also provided a downhole tubing string having a joint insulatedby a sleeve as described above. The sleeve may be secured to the tubingstring using steel straps. Sealant may be applied to edges of thesleeve. The sealant may be an additional amount of the polymer. Thedownhole tubing string may comprise tubulars as described above.

There is also provided a method of forming an insulated tubular fordownhole use, the method including the steps of providing a pipe,applying insulation around the pipe, winding a compression materialaround the insulation, and applying a polymer onto the compressionmaterial to bind to the compression material. The compression materialmay comprise 2-way tape. The compression material may comprise areinforcement material or the method may include winding a reinforcementmaterial over the compression material.

The polymer may be applied over the reinforcement material toencapsulate the reinforcement material. The reinforcement material maycomprise a wire, rope, cord or strip.

The wire, rope, cord or strip may comprise one or more of metallic wire,carbon fibre, kevlar, fibreglass, or thermoform monofilament. Theinsulation layer may comprise aerogel or any other suitable insulation.The polymer may comprise an elastomer.

There is also provided a method for forming a sleeve for wrapping aroundand insulating a joint of a downhole tubing string, the method includingproviding a mold, applying insulation around the mold, winding aninterfacing material around the insulation, and applying a polymer ontothe interfacing material to bind to the interfacing material to form thesleeve. The method may also include the step of, after the sleeve isformed, cutting the sleeve longitudinally to separate the sleeve fromthe mold. The interfacing layer may comprise 2-way tape. Reinforcementmaterial may be wound over the interfacing material.

The polymer may be applied over the reinforcement material toencapsulate the reinforcement material. The reinforcement material maycomprise a wire, rope, cord or strip. The wire, rope, cord or strip maycomprise one or more of metallic wire, carbon fibre, kevlar, fibreglass,or thermoform monofilament. The insulation layer may comprise aerogel orany other suitable insulation. The polymer may comprise an elastomer.The method may also include the step of, before applying the insulationaround the mold, applying a base layer around the mold. Applying apolymer onto the interfacing material to bind to the interfacingmaterial to form the sleeve may comprises applying the polymer to atleast an end of the sleeve to bind to the base layer at the at least theend of the sleeve.

There is also provided a method for insulating a downhole tubing string,the method including connecting tubulars to form a tubing string,wrapping an insulative sleeve around at least a joint of the tubingstring, securing the insulative sleeve around the at least a joint ofthe tubing string, and inserting the tubing string downhole. The methodsteps may be repeated for successive lengths of the tubing string. Thesleeve may be a sleeve as described above. The sleeve may be one ofplural insulative sleeves that are wrapped around multiple connectedtubulars with no substantial portions of the multiple tubulars beinguncovered by the plural insulative sleeves. The tubulars may be tubularsas described above. The sleeve may be secured to the tubing string usingsteel straps. The method may also include applying sealant to edges ofthe sleeve. The sealant may be an additional amount of the polymer.These and other aspects of the device and method are set out in theclaims.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments will now be described with reference to the figures, inwhich like reference characters denote like elements, by way of example,and in which:

FIG. 1 is a schematic section view through an insulated downholetubular.

FIG. 2 is a side view of insulated tubulars before being joined forinsertion.

FIG. 3 is a closeup schematic side cutaway view of a joint of a tubingstring showing an insulated sleeve about the joint string.

FIG. 4 is a flow diagram showing a method of insulating a downholetubing string.

FIG. 5 is a flow diagram showing a method of forming an insulatedtubular for downhole use.

FIG. 6 is a flow diagram showing a method for forming a sleeve forwrapping around and insulating a joint of a downhole tubing string.

DETAILED DESCRIPTION

Immaterial modifications may be made to the embodiments described herewithout departing from what is covered by the claims. In the claims, theword “comprising” is used in its inclusive sense and does not excludeother elements being present. The indefinite articles “a” and “an”before a claim feature do not exclude more than one of the feature beingpresent. Each one of the individual features described here may be usedin one or more embodiments and is not, by virtue only of being describedhere, to be construed as essential to all embodiments as defined by theclaims.

FIG. 1 schematically shows a tubular for downhole use, the tubularcomprising, in the innermost part of the tubular, a pipe 10, which maybe of conventional construction. An insulative cladding 20 surrounds thepipe, formed for example as follows. In this example, an insulationlayer 12 surrounds the pipe 10. An interfacing layer 14 surrounds theinsulation layer. The interfacing layer, as may other layers described,may comprise plural layers. The interfacing layer contacts theinsulation layer and a protective layer 16. The protective layer 16 maycomprise a polymer sprayed onto the interfacing layer.

There may be reinforcing material 18 within the protective layer, shownschematically as a single line though typically it would wind around thepipe.

Insulation layer may be any insulation, but is preferably an aerogel. Anaerogel is a synthetic porous ultralight material derived from a gel, inwhich the liquid component for the gel has been replaced with a gas. Theresult is a solid with extremely low density and low thermalconductivity. Aerogels can be made from a variety of chemical compounds.The aerogel should be selected to withstand downhole temperatures suchas temperatures up to ISOC or as much as 280 C.

FIG. 5 is a flow diagram showing a method of forming an insulatedtubular for downhole use. In step 80, a pipe is provided. In step 82,insulation is applied around the pipe. Insulation may be applied to theproduct in “blanket” form. The insulation may be in the form of pre-cutrectangular sheets. These sheets may then be cut them down to the sizeneeded to surround the pipe. They may then be formed, for example byhand, around the tubular. The sheets may be loosely fastened at severalpoints using adhesive tape or film, depending on tubular diameter.

In a tubular of approximately 9.6 m length there are usually 4 separatepieces of insulation blanket butt jointed and wrapped.

The insulation may also arrive on large rolls which can then be cut downto appropriate width prior to the manufacturing process.

The tape is applied tangentially to the tubular holding the insulationin place for transport to the next step, winding, as well as ensuringthe butt joints in the insulation stay together.

An adhesive may be used to secure the insulation layer to the pipe, butthis is not preferred as it negatively impacts the compaction processand can result in an unacceptably irregular product.

The initial insulation layer may be applied to the entire tubular exceptfor the ends. For example, approximately 3 ft from the box end (threadedcoupling) and 1.5 ft from the pin (threaded end) may be left bare, inorder to allowing the elevators (lifting device on the rig) and thetongs (large capacity self-locking wrenches used to assemble downholetubulars and apply torque) to grip the bare steel. This area that is notcoated during the initial process may then be covered with the pre madesleeves, described below, if the thermal demands of the customer requirefull coverage, after the threaded connection is made on site.

The interfacing layer may be a compression layer, applied to theinsulation to compress it against the pipe. In step 84 of FIG. 5 , acompression material is wound around the insulation. The interfacinglayer may include, for example an adhesive backed (2-way) fabric tape,which may be spiral wound around the insulation layer, partiallycompacting it as well as isolating it from the other layers. A plasticwrap may be used to provide a more thorough barrier, but this is notpreferred as this may result in bubbles in the outer polymer layer. Thefabric tape may have micro porosity so that the polymer has something toadhere to. Another layer that was considered was a fabric wrap aroundthe fabric tape, but this is not considered necessary as the outer layercan adequately bond to the fabric tape and no additional separation fromthe insulation is required.

In optional step 86 of FIG. 5 , a reinforcement material is wound overthe compression material. Examples of possible reinforcement materialsinclude a wire, rope, cord or strip, for example steel wire or rope, ormetal bands, or synthetic wires, ropes or bands, such as made of anaramid fibre such as Kevlar™. A wire, rope, cord or strip wound aroundthe insulation may have a spacing determined by the pipe diameter. Forexample, on a pipe 2⅜ inches in diameter, the spacing between flights ofthe wound material may be 1 h inch.

The reinforcement material may include a high tensile strength filamentand may also be spirally wound around the product further compressingthe insulation. This filament may be a metallic wire, or otherunidirectional continuous filament. Examples include carbon fibre,kevlar, fibreglass, or thermoform monofilaments.

Presently the reinforcement is wound as a single uniform layer, thismakes it easier to avoid pinching due to unbalanced pressures. The pipemay be chucked up in a lathe and an employee may traverse the lengthwith the filament spool resting on a cart, using a braking mechanism tocontrol the tension and spacing. Other approaches include a tunnelwrapper approach or a braiding machine, either of which the insulationcovered tubular will pass through as the spool or spools rotate around.The braiding machine may be used to provide the balanced pressure usingmultiple layers. The fabric tape or other compression material may bewound using the same winding station (e.g. lathe setup, tunnel wrapperor braiding machine).

The filament winding produces a rippled pattern that increases theavailable surface area for the outer coating to bond to. If the filamentchosen for the application is not of a monofilament nature then the highstrand count also increases the available surface area for the outercoating to bond to.

In step 88 of FIG. 5 , a polymer is applied onto the compressionmaterial. This may include applying the polymer onto another layeraround the compression material. This polymer may form at least part ofa protective layer of the tubular. The polymer may be, for example aphenolic resin, thermoset plastic, thermoplastic, thermoform plastics,epoxies, polyaspartics, and silicones. In an example, the polymer is anelastomer and is a thermoset plastic or thermoplastic. The polymer maybe selected to be resistant to temperatures up to 150 C, 200 C or 280 Cfor example. The outer polymer layer may be for example 50-60 mil thick.If the pipe has an outer diameter of 2⅜ inches, the insulated tubularmay have a thickness in the order of 3⅜ inches.

The polymer may be spray applied. In the case that application of thepolymer produces gases, to allow for gasses to escape during applicationof the polymer the spray pattern may be applied from either right toleft or left to right. If using an exothermic thermoset polymer,normally this heat is absorbed by the substrate and isn't an issue,though by applying this to a highly insulated substrate the heat causesany trapped air to expand. If the coating is not applied in a linearpattern this expanding hot air cannot escape and bubbles up through thecoating. With traditional coatings there is a long enough wet film timeto allow the coating to re-level itself, but if the polymer has a rapidsetup time, the coating cures while the hot gases escape resulting intunnelling down to the compression layer. By moving in one direction theexpanding gases can continue to travel through the insulation matrix toescape as opposed to travelling up through the coating. When the end ofthe tubular is reached a small amount of coating is applied to verifythat the gases are still not rushing out, and once they have stopped theend is sealed with the polymer. This left to right or right to leftpattern may be applied at the winding station.

The coating should be applied so as to fully wet out the compressionlayer as well as the reinforcing material as this then produces acomposite matrix that gives the outer coating its strength. Thiscomposite that is produced reinforces the properties of the outer layerincreasing its abrasion resistance as well as its tensile strength,ensuring the integrity of the insulation envelope during transport anddown hole installation. The coating may harden with the reinforcementmaterial already under tension.

Before insulation is applied, the pipe may be blasted to an 8-10 milprofile so that the polymer can adhere to the bare tubing. When thepolymer layer is applied, it may also be applied to the ends of theinsulated section so that it binds to the bare tubing and seals in theinsulation and otherlayers.

The above description indicates how tubulars can be insulated. To obtainfull insulated coverage, additional insulation of the tubing may becompleted after makeup is completed on the rig floor. Pre-sprayedsleeves are made up before deployment at a predetermined length to coverthe make-up distance. The sleeves can then be attached to theuninsulated connection and secured. The sleeve can then be sprayed withthe polymer to result in a fully sealed joint that will not lose heatdue to an uninsulated connection.

A sleeve may be produced using the same process as for the regularinsulation as described above, albeit on a mold, which may be a pipe oranother pipe-shaped mold, and then cut longitudinally (parallel to themold) and removed as a “C” shaped tubular sleeve.

The sleeve can then be used to insulate joints and exposed ends of thetubulars. The Sleeve is produced to a given length dictated by customerdemands. Being preformed to the diameter the tubular greatly increasesthe ease of installation.

FIG. 6 is a flow diagram showing a method for forming a sleeve forwrapping around and insulating a joint of a downhole tubing string. Instep 90, a mold is provided. In optional step 92 of FIG. 6 , a baselayer is applied around the mold. The base layer is adjacent to themold, but when the polymer is sprayed onto the outside of the sleeve instep 100, it may also be sprayed onto the ends of the sleeve so that itseals to the base layer. The base layer may extend some distance beyondthe edge of the sleeve to give more room to stick to and so that thepolymer doesn't stick to the pipe shaped mold. The optional base layermay be selected to be compatible with the polymer as the outer coatinghas to seal to it on the edges to fully encapsulate the insulation andimprove the strength of the sleeve. Once we cut the sleeve to remove itfrom the pipe shaped mold, without the base layer if care is not takenthe insulation can separate from the polymer and reinforcement matrix.While this careful handling is fine in some applications in others amore robust package needs to be created.

Sleeves have been fabricated with and without a base layer on theunderside. Because of the hydrophobic nature of the insulation fluidintrusion is usually not much of an issue. The main concern with using abase layer is to ensure cleanliness during transport and installation aswell as to ensure no metallic contamination can occur which could resultin a corrosion cell underneath the sleeve.

Using a base layer and sealing it to the polymer creates an air andwater tight envelope. In some applications fluid does not travel throughthe space between the production string and the casing tubings, and as aresult the insulation is not at risk of fluid entrapment in this area.In other production situations, where the insulated tubular is securedin place with cement, we need to fully isolate the insulation and steelsubstrates from the cement to inhibit corrosion. There are also furtherapplications where fluid is pumped down this space between the casingand production tubing and again we would want to fully insulate andprotect the steel and insulation from this liquid.

The base layer may be formed, for example of a sheet elastomer that iscompatible with the polymer top coat. For our current polymer, we useflexible pvc sheeting which provides the required moisture resistance aswell as being compatible with the system to provide an air and watertight bond.

In step 94 of FIG. 6 , insulation is applied around the mold. If thereis a base layer applying the insulation around the mold comprisesapplying the insulation around the base layer. In steps 96-100, andinterfacing material is wound around the insulation, a reinforcementmaterial is optionally wound over the interfacing material, and apolymer is applied onto the interfacing material, including thereinforcement material. In step 102, the sleeve is removed from themold. This may comprise cutting the sleeve longitudinally. FIG. 3schematically shows, not to scale, a sleeve 42 around a joint 44.

In this embodiment, a base layer 46 is shown as a single line boundinginsulation layer 12 next to pipe 10. Pipes 10 are connected at joint 44to form a tubing string 11. The base layer 46 would typically contactpipe 10 but is shown separated from pipe 10 for clarity. The base layer46 has a portion 48 that extends out from insulation layer 12 and iscontacted by protective layer 16. An interfacing layer 14 andreinforcing material 18 as shown in FIG. 1 would typically also bepresent but are omitted in this figure. A sealant 50 is shown filling agap 52 between the sleeve 42 and regular insulative cladding 20. Layersof the regular insulative cladding 20 are not shown in this figure butare shown in FIG. 1 . The sealant 50 may be formed of the same materialforming the protective layer to form a unitary outer coating. Metalbands 54 are also shown around the sleeve 42 to secure it to the pipes10.

While the sleeve 42 is shown covering the joint 44 and adjacent portionsof the pipes only, plural sleeves could also be used to cover an entiretubing string.

During installation the tubulars are connected as normal on the rigfloor.

Prior to insertion down hole but after the connection is made the sleeveis placed around the connection and then secured with stainless steelstrapping 54 (e.g. stainless steel zip ties). An alternative method canincorporate collars that can be welded or set screwed to the bare pipeabove or below the makeup area to hold the blanket in place. Ifadditional isolation is required, the edges and seams can be coated onthe rig floor by spraying an additional top coat. The top coat may bethe same material that is used for the normal outer coat, which providesa monolithic envelope and ensures the entire tubular string isinsulated. A different sealant could also be used.

FIG. 4 is a flow diagram showing a method of insulating a downholetubing string. In step 60, tubulars are connected to form a tubingstring. The tubulars can be insulated tubulars such as tubulars with aninsulative cladding as shown for example in FIG. 1 . In step 62 aninsulative sleeve, such as for example a sleeve 42 as shown in FIG. 3 ,is wrapped around at least a joint of the tubing string. In step 64, theinsulative sleeve is secured around the at least a joint. This securingmay be, for example, with metal bands as shown in FIG. 3 . In optionalstep 66, sealant is applied to edges of the sleeve, which may include alongitudinal edge where the sleeve was cut off a mold, and may includeend edges where the sleeve terminates and may contact another sleeve ora regular insulative cladding. The sealant may be an additional amountof the same material used for an outer coating of the sleeve. In step68, the tubing string is inserted downhole. Inserting the tubing stringdownhole may include, for example, progressing a tubing string that isalready partially downhole further downhole. In step 70, an additionaltubular or tubulars are obtained so that steps 60-68 can be repeated foranother length of tubing string. The step of connecting tubulars to forma tubing string may comprise connecting a tubular or tubulars to anexisting tubing string.

The thickness of the insulation may be determined after a thermalconductivity simulation has calculated the starting and exitingtemperature.

The distance that the insulation is from either the pin end and/or theupset end may be selected based on measurements of rig components, suchas slips on the rig floor, makeup tongs being used (open faced) and sliptype elevators used for pulling and holding the weight of the stringafter makeup. FIG. 2 shows an example of pipe uninsulated areadimensions in schematic form and is not to scale. In FIG. 2 , insulativecladding 20 is separated by thread gap 22 from threads 24 at a pin end26 of the pipe 10. In an example, the thread gap 22 is 12 inches. At thebox end 28, upset gap 30 between upset 32 and insulative cladding 20comprises space 34 for slips 36 and an additional uncovered gap 38between the top of slips 36 and upset 32. In an example, the upset gap30 is 44 inches with 19 inches of space 34 allowed for slips 36 and theadditional uncovered gap 38 being 25 inches. If slip-type elevators areused, additional space, for example 14 additional inches, may berequired. Rig floor 40 is also shown in this figure with slips 36between rig floor 40 and pipe 10.

The embodiments of the invention in which an exclusive property ofprivilege is claimed are defined as follows:
 1. A method for forming asleeve for wrapping around and insulating a joint of a downhole tubingstring, the method comprising: providing a mold; applying an insulationaround the mold; winding an interfacing material around the insulation;winding a wire, rope, cord or strip or a combination thereof over theinterfacing material to provide a reinforcement material; and applying apolymer onto the interfacing material and the reinforcement material tobind to the interfacing material and to encapsulate the reinforcementmaterial to form the sleeve.
 2. The method of claim 1, furthercomprising: cutting the sleeve longitudinally to separate the sleevefrom the mold after the sleeve is formed.
 3. The method of claim 1,wherein the interfacing material comprises 2-way tape.
 4. The method ofclaim 1, wherein the wire, rope, cord or strip, or the combinationthereof comprises one or more of metallic wire, carbon fibre, Kevlar,fiberglass, or thermoform monofilament.
 5. The method of claim 1,wherein the insulation comprises aerogel.
 6. The method of claim 1,wherein the reinforcement material is spirally wound around theinterfacing layer to provide a rippled pattern that increases theavailable surface area for bonding to the polymer.
 7. The method ofclaim 6, wherein the reinforcement material spirally wound around theinterfacing layer has a spacing between flights.
 8. The method of claim6, wherein the reinforcement material spirally wound around theinterfacing layer compresses the interfacing layer.
 9. The method ofclaim 1, wherein the polymer is a phenolic resin polymer, a thermosetplastic polymer, a thermoplastic polymer, a thermoform plastic polymer,an epoxy polymer, a polyaspartic polymer, a silicone polymer, or anelastomeric polymer.
 10. The method of claim 1, wherein the mold ispipe-shaped.
 11. A method for forming a sleeve for wrapping around andinsulating a joint of a downhole tubing string, the method comprising:providing a mold; applying a sheet elastomer around the mold as a baselayer; applying an insulation around the base layer on the mold; windingan interfacing material around the insulation; and applying a polymeronto the interfacing material to bind the interfacing material to formthe sleeve; wherein the step of applying the polymer onto theinterfacing material to bind to the interfacing material to form thesleeve comprises applying the polymer to at least an end of the sleeveto bind to the base layer at the at least the end of the sleeve; andwherein the sheet elastomer is compatible with the polymer.
 12. Themethod of claim 11, wherein a reinforcement material is spirally woundaround the interfacing material to provide a rippled pattern thatincreases the available surface area for bonding to the polymer.
 13. Themethod of claim 12, wherein the reinforcement material spirally woundaround the interfacing material has a spacing between flights.
 14. Themethod of claim 12, wherein the reinforcement material spirally woundaround the interfacing material compresses the interfacing material. 15.The method of claim 12, wherein the polymer is a phenolic resin polymer,a thermoset plastic polymer, a thermoplastic polymer, a thermoformplastic polymer, an epoxy polymer, a polyaspartic polymer, a siliconepolymer, or an elastomeric polymer.
 16. A sleeve for wrapping around andinsulating a joint of a downhole tubing string, the sleeve produced bythe method of claim
 1. 17. A method for insulating a tubing string, themethod comprising: connecting a plurality of insulated tubulars to forman insulated tubing string; wrapping the sleeve of claim 16 around oneor more joints of the tubing string; and securing the sleeve around thejoints of the tubing string.
 18. The method of claim 17, furthercomprising the step of securing the sleeve around the joints withstainless steel strapping.
 19. The method of claim 17, furthercomprising attaching collars above or below the sleeve to hold thesleeve in place.
 20. The method of claim 17, further comprising applyingsealant to edges of the sleeve.